The present embodiments generally relate to the vaporization of cryogenic fluids such as oxygen, nitrogen and liquefied natural gas (LNG) using ambient air vaporizers and to control atmospheric fog that is generated by the exiting cold air stream as it mixes with the surrounding humid ambient air.
As the need for larger cryogenic vaporizer systems has developed and the advantage of obtaining the required heat for the vaporization process from the ambient air has been recognized multiple arrays of ambient air vaporizers are employed and have been found to create fog banks which are both objectionable and hazardous.
It has further been found that large arrays of ambient air cryogenic fluid vaporizers have the potential to cool a large body of the ambient air surrounding the vaporizers on calm, no wind days. Since the ambient air vaporizers require a supply of the warmer ambient air, the cool air, since it is heavier than the surrounding warmer air tends to sink or travel to the ground where if mixed with surrounding warm air as it enters the vaporizer, will reduce vaporizer performance.
Prior ambient air cryogenic vaporizer art, such as, Brown in U.S. Pat. No. 7,870,747B1, Jan. 18, 2011; Brown in U.S. Pat. No. 7,493,772B1, Feb. 24, 2009; Coyle in US APPL 2009/0211263A1; White in U.S. Pat. No. 5,390,500, 2/1995 and Vogler in U.S. Pat. No. 4,399,660, 8/1983 do not appreciate the natural downward flow direction of the cooling ambient air which is heavier than the surrounding mass of the warmer ambient air. The cooler, heavier air forms a “ground air layer” beneath the moist warmer air, thus forming a ground fog as the cool lower air layer cools the warmer upper layer forming a fog bank at ground level where it is considered hazardous, while at the same time the cool air collecting around the vaporizer will considerably reduce performance to unacceptable levels.
As the arrays of ambient air vaporizers have become larger, so to has the height of the vaporizer increased to provide as much vaporization capacity into as small a plot space as possible. One method to save space has been to use ducted ambient air vaporizers which employ fans or blowers to force the required air over the vaporizing, finned tubular heat exchange elements. These high velocity fans require considerable and costly power which reduces the benefit of the ambient vaporizer over energy consuming heated type vaporizers.
For the foregoing reasons there is a need for an ambient air vaporizer system which well reduce or eliminate fog, which will preclude the recycling of cooled air into the warm entering air stream to the vaporizer array and will permit the free flow of air through the vaporizer system and in certain cases to provide an induced draft warm ambient air supply to the vaporizer array to enhance the air flow through the system and increase vaporizer capacity.